Which Smarty, JR or SR?
If SR(w/standard revo software), I would not exceed SW3 if towing, you may slip your stock clutch even then.
Excuse my ignorance on the Edge Juice, is it a fuel box(like tst) ? Or is it a downloader(like bullydog)? If it's a fuel box, I see no problem leaving it on zero and just utilizing it for the attitude monitor. If it's a downloader, I would not mix programmers, likely to contaminate your ECM.
The Smarty is a downloader, it reprograms your ecm. I stack my TST(fuel box) on top of the Smarty in very small increments and only on the top end(power only on tst). I also stack my EZ for pressure, I am not fond of Smarty's pressure feature, seems irratic on my truck.
Whenever you utilize more than one performance box/programmer at a time, you run the risk of too much timing, so proceed with moderation and monitor the different settings.
Hope that helps a bit, Jess